The present invention relates to a three-way valve assembly for a storage tank of a reverse osmosis water purifier which includes a meter for measuring the current quantity of water in the pressure tank of the water purifier.
Reverse osmosis water purifiers are widely accepted for industrial as well as home uses. FIG. 1 illustrates an installation of a reverse osmosis water purifier, in which water from a water tap 10 is pumped into a water filter unit 12 by a water pump 11, and purified water is delivered from the water filter unit 12 into a pressure tank 14 through a purified water delivery tube 13. The pressure tank 14 is filled with compressed air to squeeze an inflatable water container 15, as seen in FIG. 2, which has an outlet connected to the purified water delivery tube 13. There is provided a pressure regulator 17 on the purified water delivery tube 13, which automatically turns off the water pump 11 as the inflatable water container 15 is fully filled up with purified water, or turns on the water pump 11 letting it to pump water into the water filter unit 12 as the inflatable water container 15 is on low level. This structure of reverse osmosis water purifier has no means to measure the operation time in increasing the water pressure inside the pressure tank 14 from the low level to the high level. Under normal conditions, increasing the water pressure inside the pressure tank 14 from zero reading (zero water level) to high-water level (full load) requires a certain length of operation time. When a relative longer time was taken to fill the inflatable water container 15 of the pressure tank 14 to high-water level, it means that the system of the reverse osmosis water purifier is abnormal, and the filter element, the water piping, the water pump 11, as well as the water tap 10 should be checked. If the reverse osmosis water purifier is abnormal, water still will flow out of the water outlet 16 during the operation of the system even when it is opened and even if the pressure tank 14 is at zero water level. Therefore, an user can not know the current water level in the inflatable water container 15 inside the pressure tank 14.